This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-260614, filed Sep. 14, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a semiconductor device having a sealing film formed on the surface having columnar electrodes, which are connected to electrode pads of the semiconductor device, formed thereon and a method of manufacturing the same.
A method of forming columnar electrodes connected to electrode pads formed in a semiconductor device and Bonding the semiconductor device to a circuit board via the columnar electrodes is known to the art as a face down bonding method. The face down bonding method is advantageous in that a semiconductor device can be bonded in its size, making it possible to miniaturize the apparatus, compared with QFP (Quad Flat Package). In the face down bonding method, however, the step of pouring a liquid sealing resin into the clearance between the semiconductor device and the circuit board after the bonding step takes time, leading to low productivity. To overcome this difficulty, a method of forming a sealing film on the surface having columnar electrodes of a semiconductor device formed thereon is now under study. FIGS. 15 to 17 collectively exemplify the particular conventional method.
In the first step, a semiconductor substrate 1 such as a wafer state silicon substrate having a plurality of columnar electrodes 2 formed thereon is prepared, followed by forming by a molding method or a spin coating method a sealing film 3 on the upper surface of the semiconductor substrate 1 having the columnar electrodes 2 formed thereon, as shown in FIG. 15. Therefore, the upper surfaces of the columnar electrodes 2 are covered with the sealing film 3 in this state. Then, the upper surface of the sealing film 3 is polished or etched appropriately so as to expose the upper surfaces of the columnar electrodes 2, as shown in FIG. 16. Further, solder balls 4 are formed on the upper surfaces of the columnar electrodes 2, as shown in FIG. 17. Finally, a dicing treatment is applied to separate the wafer to individual semiconductor devices.
Where the sealing film 3 is formed by a molding method, complex process steps and costly apparatuses are required. Further, the molding method gives rise to an additional problem that the semiconductor substrate 1 tends to be deformed by the heating so as to bring about a large unevenness in the height of the columnar electrodes 2. On the other hand, where the sealing film 3 is formed by a spin coating method, it is necessary to use a liquid sealing resin having a relatively low viscosity, with the result that a large difference in the linear expansion coefficient is brought about between the sealing film 3 and the semiconductor substrate 1. As a result, when stress derived from the difference in the linear expansion coefficient is generated between the sealing film 3 and the semiconductor substrate 1, cracks are generated between the columnar electrodes 2 and the solder balls 4.
An object of the present invention is to provide a method of manufacturing a semiconductor device, which permits using a relatively cheap apparatus and also permits using a liquid sealing resin having a relatively high viscosity.
According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of:
preparing a semiconductor substrate having a plurality of columnar electrodes formed apart from each other on one main surface;
loading a warmed liquid sealing resin between adjacent columnar electrodes on at least one main surface of the semiconductor substrate; and
cooling the liquid sealing resin so as to solidify the sealing resin to. form a sealing film on the one main surface of the semiconductor substrate.
According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of:
preparing a semiconductor substrate having a plurality of columnar electrodes formed apart from each other on one main surface;
arranging a printing mask on the semiconductor substrate;
heating the semiconductor substrate and the printing mask to a predetermined temperature;
supplying a liquid sealing resin onto the printing mask so as to have the liquid sealing resin warmed by the printing mask; and
loading the warmed liquid sealing resin into the clearance between adjacent columnar electrodes formed on one main surface of the semiconductor substrate so as to form a sealing film.
According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of:
preparing a semiconductor substrate having a plurality of columnar electrodes formed apart from each other on one main surface;
arranging a mask on one main surface of the semiconductor substrate;
printing a liquid sealing resin on the one main surface of the semiconductor substrate from above the mask by using a squeegee so as to form a sealing film loaded in the clearance between adjacent columnar electrodes; and
measuring the weight of the semiconductor substrate having the sealing film formed thereon so as to judge whether or not the thickness of the sealing film is appropriate.
Further, according to a fourth aspect of the present invention, there is provided a semiconductor device, comprising:
a semiconductor substrate having a plurality of columnar electrodes formed thereon apart from each other; and
a sealing film formed on one main surface of the semiconductor substrate so as to be loaded in the clearance between adjacent columnar electrodes;
wherein the upper surface of the sealing film is substantially flush with the upper surface of the columnar electrode in the vicinity of the columnar electrode and is most recessed in substantially the central portion between adjacent columnar electrodes.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.